Research Document - 2011/107
Recovery Potential Assessment for the Umatilla Dace (Rhinichthys Umatilla)
By B. Harvey and T. Brown
Abstract
Dace are minnows belonging to the Order Cypriniformes. Adult Umatilla Dace Rhinichthys Umatilla are usually under 10 cm in fork length, with morphology intermediate between that of speckled and leopard dace, implying that Umatilla Dace is the result of hybridization between the other two species. Umatilla Dace was designated Special Concern by COSEWIC in 1988, and was included on Schedule 3 of the Species at Risk Act (SARA) in 2004. In April 2010 the species was assessed as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) based on the limited area of occupancy, <10 locations, and the expected future loss of habitat or deterioration of habitat quality due to potential threats.
Umatilla Dace in Canada are found at the upper limits of their global distribution and the Canadian distribution represents only 5% of the total global distribution. The length of time they have occupied this area is unknown, nor is how their occupancy of a fringe area of the overall range relates to adaptability. In Canada, the species’ occurrence is limited to the Similkameen River, Tulameen River, Columbia River below the HLK Dam, Kootenay River below Bonnington Falls, lower Slocan River, lower Pend d’Oreille River, and the Kettle River below Cascade Falls. There have been no new surveys for Umatilla Dace for most of their range within the past 20 years (around five generations); there is therefore great uncertainty about persistence of the species in some watersheds. In the light of such significant uncertainties, setting numerical “recovery targets” is impossible. The logical next step is to fill data gaps, starting with annual sampling using consistently applied methods in enough locations to provide a better understanding of distribution and recent population trajectories. The minimum level at which the population would be considered recovered is when its risk assessment status changes from Threatened to Special Concern. Such a change would require addressing and clarifying some of the assumptions and uncertainties within the COSEWIC report, or the elimination, reduction or mitigation of potential threats to habitat quality that were given as reasons for the threatened designation by COSEWIC in 2010. Downgrading to Special Concern would not, however, mean that management actions were not required.
Threats to Umatilla Dace in the Canadian portion of its global range include; hydroelectric development, flow changes related to existing dam operations, introductions of alien species, water extraction, resource extraction, land use (agriculture, transportation corridors, timber harvest) and scientific over-sampling. Allowable harm to Umatilla Dace in the Similkameen River, in the limited Kettle River habitat below Cascade Falls, and in the Columbia, Kootenay and Slocan Rivers should include scientific sampling for the purpose of further understanding abundance, distribution, and habitat use of the species, but total harm should not increase beyond current levels.
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